1. Field of the Invention
The present invention relates to an automatic balancing structure of a medical balancing stand.
2. Description of Related Art
The medical balancing stand is used to support and suspend a medical device such as a surgical microscope at an optional position in midair. The medical balancing stand includes a vertical arm and a lateral arm. A first end of the lateral arm supports a relatively heavy load such as a surgical microscope and a second end of the lateral arm supports a counterweight to balance the load. An intermediate part of the lateral arm is provided with a turn shaft that is horizontally supported with the vertical arm so that the lateral arm is able to turn relative to the vertical arm.
The turn shaft has a clutch unit that is locked in a normal state to prevent the lateral arm from turning relative to the vertical arm. When moving the load (for example, a surgical microscope) supported at the first end of the lateral arm to an optional height position, an operator who may be a doctor releases the clutch unit and turns the surgical microscope together with the lateral arm. The lateral arm having the surgical microscope is balanced on the turn shaft due to the counterweight, and therefore, stops at an optional turned position in midair as if in a gravity-free state even if the operator removes his or her hands from the surgical microscope. Accordingly, the operator is able to freely change the position of the surgical microscope in midair. Once the position and orientation of the surgical microscope are optimized as required, the operator locks the clutch unit to fix the lateral arm at the position.
Balance of the lateral arm on the turn shaft is detected and adjusted with the use of an encoder that detects a turn angle of the turn shaft and a computer that adjusts the counterweight according to a signal from the encoder. In connection with this, a related art is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2005-52679.